In a motor vehicle, a fuel for an internal combustion engine can be conveyed or pumped by means of a high-pressure injection system. A high-pressure injection system of this kind has a high-pressure pump which can convey the fuel toward the internal combustion engine on a high-pressure side with a pressure of greater than 200 bar. The fuel pump can have a piston which is moved back and forth between a bottom dead center and a top dead center in a compression chamber or swept volume. To this end, the piston can be driven, for example, by an engine shaft of the internal combustion engine. A complete cyclical movement of the piston is referred to as the pump cycle here.
As part of the piston movement from the top dead center to the bottom dead center, an opening movement of an inlet valve of the high-pressure pump begins, in each pump cycle, starting from a specific opening position of the piston. This is then the beginning of an intake phase in which fuel or, in general, a fluid flows into the compression chamber through the inlet valve. After the bottom dead center is reached, the intake phase ends and the piston is moved back toward the top dead center.
During this expulsion phase, the fluid is expelled from the compression chamber again by the movement of the piston toward the top dead center. Provided that the inlet valve is open in this case, the fluid flows back to a low-pressure side through the inlet valve. Therefore, the inlet valve is closed by a control device by current being applied to an electromagnet during the movement of the piston toward the top dead center. This occurs at a piston position which is dependent on a setpoint value for the fluid pressure to be adjusted to on the high-pressure side. The electromagnet to which current is applied magnetically attracts an armature which is connected to the inlet valve, so that said valve is carried along. When the inlet valve is closed, the fluid is no longer expelled through the inlet valve, but rather through an outlet valve, owing to the piston movement. The outlet valve may be, for example, a non-return valve. The fluid which is expelled through the outlet valve generates the fluid pressure on the high-pressure side downstream of the outlet valve.
Downstream of the outlet valve, there is arranged a pressure sensor which generates a sensor signal which is intended to indicate the fluid pressure. In a manner dependent on the sensor signal, the control device can then specifically set said piston position for the closing of the inlet valve, that is to say for the application of current to the electromagnet during the expulsion phase, and hereby adjust the fluid pressure to the setpoint pressure or setpoint value. This however assumes that the sensor signal of the pressure sensor correctly signals the fluid pressure. By contrast, if the pressure sensor is defective and always signals too low a pressure by means of the signal sensor, for example a zero signal, then the control device will always further increase the actual fluid pressure, because there is no resulting reduction in the control deviation (setpoint value minus sensor signal). This can lead to damage to the high-pressure injection system, for example to bursting or rupturing of a fluid line or of a seal.